Conductive and Hydrophilic Bipolar Plate Coatings and Method of Making the Same

ABSTRACT

A flow field plate for fuel cell applications includes a metal with a carbon layer disposed over at least a portion of the metal plate. The carbon layer is overcoated with a titanium oxide layer to form a titanium oxide/carbon bilayer. The titanium oxide/carbon bilayer may be activated to increase hydrophilicity. The flow field plate is included in a fuel cell with a minimal increase in contact resistance. Methods for forming the flow field plates are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. application entitled“Carbon Based Bipolar Plate Coatings for Effective Water Management”being filed concurrently herewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an electrically conductivefluid distribution plate, a method of making an electrically conductivefluid distribution plate, and systems using an electrically conductivefluid distribution plate according to the present invention. Morespecifically, the present invention is related to the use of anelectrically conductive fluid distribution plate in addressing contactresistance difficulties in fuel cells and other types of devices.

2. Background Art

Fuel cells are used as an electrical power source in many applications.In particular, fuel cells are proposed for use in automobiles to replaceinternal combustion engines. A commonly used fuel cell design uses asolid polymer electrolyte (“SPE”) membrane or proton exchange membrane(“PEM”) to provide ion transport between the anode and cathode.

In proton exchange membrane type fuel cells, hydrogen is supplied to theanode as fuel and oxygen is supplied to the cathode as the oxidant. Theoxygen can either be in pure form (O₂) or air (a mixture of O₂ and N₂).PEM fuel cells typically have a membrane electrode assembly (“MEA”) inwhich a solid polymer membrane has an anode catalyst on one face, and acathode catalyst on the opposite face. The anode and cathode layers of atypical PEM fuel cell are formed of porous conductive materials, such aswoven graphite, graphitized sheets, or carbon paper to enable the fuelto disperse over the surface of the membrane facing the fuel supplyelectrode. Each electrode has finely divided catalyst particles (forexample, platinum particles), supported on carbon particles, to promoteoxidation of hydrogen at the anode and reduction of oxygen at thecathode. Protons flow from the anode through the ionically conductivepolymer membrane to the cathode where they combine with oxygen to formwater, which is discharged from the cell. The MEA is sandwiched betweena pair of porous gas diffusion layers (“GDL”), which in turn aresandwiched between a pair of non-porous, electrically conductiveelements or plates. The plates function as current collectors for theanode and the cathode, and contain appropriate channels and openingsformed therein for distributing the fuel cell's gaseous reactants overthe surface of respective anode and cathode catalysts. In order toproduce electricity efficiently, the polymer electrolyte membrane of aPEM fuel cell must be thin, chemically stable, proton transmissive,non-electrically conductive and gas impermeable. In typicalapplications, fuel cells are provided in arrays of many individual fuelcell stacks in order to provide high levels of electrical power.

In general, bipolar plates for fuel cell applications need to becorrosion resistant, electrically conductive, and have a low contactangle for effective water management. Metals such as stainless steel aretypically used for bipolar plates because of their mechanical strengthand ability to be stamped. However, such metals often have a passiveoxide film on their surfaces requiring electrically conductive coatingsto minimize the contact resistance. Such electrically conductivecoatings include gold and polymeric carbon coatings. Typically, thesecoatings require expensive equipment that adds to the cost of thefinished bipolar plate. Moreover, metallic bipolar plates are alsosubject to corrosion during operation. The degradation mechanismincludes the release of fluoride ions from the polymeric electrolyte.Metal dissolution of the bipolar plates typically results in release ofiron, chromium and nickel ions in various oxidation states.

For water management, it is desirable for metal bipolar plates to have alow contact angle at the bipolar plate/water border; that is, a contactangle less than 40°. Titanium nitride coatings have been proposed ascorrosion-resistant plating for bipolar plates. Although titaniumnitride coatings are cost-effective, such coatings do not providesatisfactory protection for the bipolar plate material. Further,titanium nitride coatings develop relatively low water affinity with acontact angle close to 60°.

Accordingly, there is a need for improved methodology for lowering thecontact resistance at the surfaces of bipolar plates used in fuel cellapplications.

SUMMARY OF THE INVENTION

The present invention solves one or more problems of the prior art byproviding in at least one embodiment a flow field plate for use in afuel cell. The flow field plate of this embodiment comprises a metalplate having a first surface and a second surface. The first surfacedefines a plurality of channels for directing flow of a first gaseouscomposition. A carbon layer is disposed over at least a portion of themetal plate while a titanium oxide layer is disposed over at least aportion of the carbon layer to form a titanium oxide-coated carbonbilayer.

In at least one embodiment, the titanium oxide-coated carbon bilayer hasa surface with a contact angle less than about 30 degrees and a contactresistance of less than 40 mohm-cm² when the flow field plate issandwiched between carbon papers at 200 psi.

In another embodiment, a fuel cell incorporating the flow field plateset forth above is provided. The fuel cell includes a first flow fieldplate with a titanium oxide-coated carbon bilayer. A first catalystlayer is disposed over the first flow field plate. An ion conductorlayer is disposed over the first flow field plate and a second catalystlayer over the ion conductor layer. Finally, a second flow field plateis disposed over the second catalyst layer. Gas diffusion layers areprovided as needed.

In still another embodiment, a method for forming the flow field plateset forth above is provided. The method comprises depositing a carbonlayer on a metallic plate followed by deposition of a titanium oxidelayer over the carbon layer to form a titanium oxide-coated carbonbilayer.

Other exemplary embodiments of the invention will become apparent fromthe detailed description provided hereinafter. It should be understoodthat the detailed description and specific examples, while disclosingexemplary embodiments of the invention, are intended for purposes ofillustration only and are not intended to limit the scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will become more fullyunderstood from the detailed description and the accompanying drawings,wherein:

FIG. 1A provides a cross sectional view of a fuel cell incorporating anexemplary embodiment of a titanium oxide/carbon bilayer on a unipolarplate;

FIG. 1B provides a cross sectional view of a fuel cell incorporating anexemplary embodiment of a titanium oxide/carbon bilayer on a bipolarplate;

FIG. 2 provides a cross sectional view of a bipolar plate channel coatedwith a titanium oxide/carbon bilayer;

FIG. 3 provides a cross sectional view of a fuel cell incorporatinganother exemplary embodiment of a titanium oxide/carbon bilayer on abipolar plate;

FIG. 4 provides a cross sectional view of a bipolar plate channel coatedwith a plurality of titanium oxide/carbon layers;

FIGS. 5A-5B provide a flowchart illustrating an exemplary method formaking a bipolar plate coated with a titanium oxide/carbon bilayer; and

FIG. 6 is a schematic illustration of a sputtering system used todeposit carbon and titanium oxide layers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to presently preferredcompositions, embodiments and methods of the present invention, whichconstitute the best modes of practicing the invention presently known tothe inventors. The Figures are not necessarily to scale. However, it isto be understood that the disclosed embodiments are merely exemplary ofthe invention that may be embodied in various and alternative forms.Therefore, specific details disclosed herein are not to be interpretedas limiting, but merely as a representative basis for any aspect of theinvention and/or as a representative basis for teaching one skilled inthe art to variously employ the present invention.

Except in the examples, or where otherwise expressly indicated, allnumerical quantities in this description indicating amounts of materialor conditions of reaction and/or use are to be understood as modified bythe word “about” in describing the broadest scope of the invention.Practice within the numerical limits stated is generally preferred.Also, unless expressly stated to the contrary: percent, “parts of,” andratio values are by weight; the term “polymer” includes “oligomer,”“copolymer,” “terpolymer,” and the like; the description of a group orclass of materials as suitable or preferred for a given purpose inconnection with the invention implies that mixtures of any two or moreof the members of the group or class are equally suitable or preferred;description of constituents in chemical terms refers to the constituentsat the time of addition to any combination specified in the description,and does not necessarily preclude chemical interactions among theconstituents of a mixture once mixed; the first definition of an acronymor other abbreviation applies to all subsequent uses herein of the sameabbreviation and applies mutatis mutandis to normal grammaticalvariations of the initially defined abbreviation; and, unless expresslystated to the contrary, measurement of a property is determined by thesame technique as previously or later referenced for the same property.

It is also to be understood that this invention is not limited to thespecific embodiments and methods described below, as specific componentsand/or conditions may, of course, vary. Furthermore, the terminologyused herein is used only for the purpose of describing particularembodiments of the present invention and is not intended to be limitingin any way.

It must also be noted that, as used in the specification and theappended claims, the singular form “a,” “an,” and “the” comprise pluralreferents unless the context clearly indicates otherwise. For example,reference to a component in the singular is intended to comprise aplurality of components.

Throughout this application where publications are referenced, thedisclosures of these publications in their entireties are herebyincorporated by reference into this application to more fully describethe state of the art to which this invention pertains.

The terms “roughness average” or “surface roughness average” as usedherein means arithmetic average of the absolute values of the profileheight deviations. The roughness average may be determined in accordancewith ANSI B46.1. The entire disclosure of this reference is herebyincorporated by reference.

In an embodiment of the present invention, a flow field plate for use infuel cell applications is provided. The flow field plate of thisembodiment comprises a metal plate with a titanium oxide-coated carbonbilayer disposed over at least a portion of the metal plate. Thetitanium oxide-coated carbon bilayer has a surface with a contact angleless than about 30 degrees and a contact resistance of less than 40mohm-cm² when the flow field plate is sandwiched between carbon papersat 200 psi. The present embodiment encompasses both unipolar and bipolarplates.

With reference to FIGS. 1A and 1B, a schematic cross section of fuelcells incorporating the flow field plates of this embodiment isprovided. Fuel cell 10 includes flow field plates 12, 14. Typically,flow field plates 12, 14 are made from a metal such as stainless steel.Flow field plate 12 includes surface 16 and surface 18. Surface 16defines channels 20 and lands 22. FIG. 1A provides a depiction in whichflow field plate 12 is a unipolar plate. FIG. 1B provides a depiction inwhich flow field plate 12 is a bipolar plate. In this variation, surface18 defines channels 24 and lands 26. Similarly, flow field 14 includessurface 30 and surface 32. Surface 30 defines channels 36 and lands 38.FIG. 1A provides a depiction in which flow field plate 14 is a unipolarplate. FIG. 1B provides a depiction in which surface 32 defines channels40 and lands 42.

Still referring to FIGS. 1A and 1B, carbon layer 50 is disposed over andcontacts surface 16. Titanium oxide layer 52 is disposed over carbonlayer 50 to form titanium oxide/carbon bilayer 54. Carbon layer 50 maybe amorphous, crystalline, or a combination thereof. Typically, thecombined thickness of titanium oxide/carbon bilayer 54 is less than 200nm. In another refinement, the combined thickness of titaniumoxide/carbon bilayer 54 is less than 100 nm. In still another variation,the combined thickness of titanium oxide/carbon bilayer 54 is greaterthan about 10 nm. In yet another refinement, the combined thickness oftitanium oxide/carbon bilayer 54 is greater than about 30 nm. In yetanother variation, the combined thickness of titanium oxide/carbonbilayer 54 is from about 20 nm to about 80 nm. In a variation, titaniumoxide/carbon bilayer 54 includes surface 56 having a contact angle lessthan about 40 degrees. The present embodiment is distinguished from theprior art methods that use hydrocarbon-containing silane coupling agentsto produce hydrophilic coatings in that the titanium oxide layerincludes hydrocarbons in an amount that is less than about 40 weightpercent of the total weight of the titanium oxide layer. In anotherrefinement, the titanium oxide layer includes hydrocarbons in an amountthat is less than about 20 weight percent of the total weight of thetitanium oxide layer. In still another refinement, the titanium oxidelayer includes hydrocarbons in an amount that is less than about 10weight percent of the total weight of the titanium oxide layer. In yetanother refinement, the titanium oxide layer includes hydrocarbons in anamount that is less than about 50 weight percent of the total weight ofthe titanium oxide layer. In this context, the term “hydrocarbons”refers to any moiety having a carbon hydrogen bond.

In a variation of the present embodiment, titanium oxide/carbon bilayer54 is only deposited on the walls of the channels and not on the lands.In another variation, the titanium layer is only deposited on the wallsof the channels while the carbon layer may be deposited on the lands.

Still referring to FIGS. 1A and 1B, fuel cell 10 further includes gasdiffusion layer 60 and catalyst layers 62, 64. Polymeric ion conductivemembrane 70 is interposed between catalyst layers 62, 64. Finally, fuelcell 10 also includes gas diffusion layer 72 positioned between catalystlayer 64 and flow field plate 14.

In a variation of the present invention, a first gas is introduced intochannels 20 and a second gas is introduced into channels 36. Channels 20direct the flow of the first gas and channels 36 direct the flow of thesecond gas. In a typical fuel cell application, an oxygen-containing gasis introduced into channels 20 and a fuel is introduced into channels36. Examples of useful oxygen containing gases include molecular oxygen(e.g., air). Examples of useful fuels include, but are not limited to,hydrogen. When an oxygen-containing gas is introduced into channels 20,water is usually produced as a by-product, which must be removed viachannels 20. In this variation, catalyst layer 62 is a cathode catalystlayer and catalyst layer 64 is an anode catalyst layer.

With reference to FIG. 2, a magnified cross sectional view of channel 20is provided. Surfaces 80, 82, 84 of titanium oxide layer/carbon bilayer54 provide exposed surfaces in channel 20. Advantageously, thesesurfaces of titanium oxide layer/carbon bilayer 54 are hydrophilic,having a contact angle less than about 40 degrees. In anotherrefinement, the contact angle is less than about 30 degrees. In stillanother refinement, the contact angle is less than about 20 degrees. Inyet another refinement, the contact angle is less than about 10 degrees.The hydrophilic nature of titanium oxide layer/carbon bilayer 54prevents water from agglomerating in channels 20. In a refinement of thepresent embodiment, the hydrophilicity of titanium oxide layer/carbonbilayer 54 is improved by activating surface 56 (i.e., surfaces 80, 82,84, 86). In a variation of the present embodiment, the surface isactivated by a ultraviolet (UV) or plasma (e.g., RF plasma, DC plasma,microwave plasma, hot filament plasma, open air plasma, and the like).In one refinement, the activation is accomplished by exposing titaniumoxide layer/carbon bilayer 54 to a UV source where the low band gap oftitanium oxide 3 to 3.2 eV absorbs UV radiation and causes electrons tojump into the conduction band creating positive holes in valence bands.This known photocatalytic ability of titanium oxide under UV activationmakes it capable of not only keeping the surface hydrophilic but alsooxidizing organic residues and keeping surfaces permanently clean.Accordingly, such layers are hydrolytically stable under typical fuelcell operating conditions.

In another refinement, the post treatment is accomplished by exposingthe titanium oxide/carbon bilayer to reactive gases such as nitrogen,nitrous oxide, nitrogen dioxide, ammonia or mixtures thereof, whichactivate the titanium oxide layer/carbon bilayer by breaking bonds andforming nitrogen-based derivatives like amines, amide, and diazofunctional groups. Accordingly, the post-treatment activation is able toincrease the amounts of nitrogen in titanium oxide layer/carbon bilayer54. This further refines the photocatalytic oxidation of titanium oxidein visible range without requiring any UV activation sources. In anotherrefinement, the titanium oxide/carbon bilayer is activated by visiblelight after treatment with a nitrogen-containg gas. In still anotherrefinement, the activation of surface 56 results in an increase inporosity as compared to the surface prior to activation. In a furtherrefinement, surface 56 includes regions in which there are at least 10pores per cm² of surface area. Moreover, surface 56 includes on averageat least 5 pores per cm² of surface area. The number of pores per cm² iscalculated by counting the number of pores in a given area observed in ascanning electron micrograph.

The porosity of titanium oxide layer/carbon bilayer 54 is alsocharacterized by the roughness average of surface 56. In a variation,the roughness average of surface 56 is from about 200 to about 1000 nm.In another variation, the roughness average of surface 56 is from about300 to about 900 nm. In still another variation, the roughness averageof surface 56 is from about 400 to about 700 nm.

In a variation, the carbon layer of the present invention iselectrically conductive. The electrical conductivity of carbon layer 50is such that the contact resistance of fuel cell 10 is less than about20 mohm-cm². In a variation of an exemplary embodiment, carbon layer 50is doped in order to increase the electrical conductivity. In onerefinement, carbon layer 50 is doped. In a further refinement, thedopant is a metal. Examples of suitable metal dopants include, but arenot limited to, Pt, Ir, Pd, Au, Ag, Co, Fe, Cu, Si, Ti, Zr, Al, Cr, Ni,Nb, Zr, Hb, Mo, W, and Ta. In another refinement, the dopant is anonmetal such as nitrogen.

With reference to FIG. 3, a schematic cross section illustratingadditional surfaces of fuel cell bipolar plates coated with titaniumoxide/carbon bilayers is provided. In this variation, one or more ofsurfaces 18, 30, and 32 are coated with a carbon layer 50. As set forthabove, in connection with the description of FIGS. 1A and 1B, fuel cell10 includes flow field plates 12, 14. Bipolar plate 12 includes surface16 and surface 18. Surface 16 defines channels 20 and lands 22. Surface18 defines channels 24 and lands 26. Similarly, bipolar plate 14includes surface 30 and surface 32. Surface 30 defines channels 36 andlands 38. Surface 32 defines channels 40 and lands 42.

Still referring to FIG. 3, carbon layer 50 is disposed over and contactssurface 16. Titanium oxide layer 52 is disposed over carbon layer 50 toform titanium oxide layer/carbon bilayer 54. In a variation, titaniumoxide layer/carbon bilayer 54 includes surface 56 having a contact angleless than about 40 degrees. In a refinement, the contact angle is lessthan 20 degrees. In still another refinement, the contact angle is lessthan 10 degrees. Similarly, titanium oxide layer/carbon bilayer 90 isdisposed over and contacts surface 18, carbon layer 92 is disposed overand contacts surface 30, and carbon layer 94 is disposed over andcontacts surface 32. Fuel cell 10 further includes gas diffusion layer60 and catalyst layers 62, 64. Polymeric ion conductive membrane 70 isinterposed between catalyst layers 62, 64. Finally, fuel cell 10 alsoincludes gas diffusion layer 72 positioned between catalyst layer 64 andbipolar plate 14. The details of titanium oxide layer/carbon bilayer 90,92, 94 are the same as for titanium oxide layer/carbon bilayer 54 whichis set forth above in connection with the description of FIGS. 1A and1B.

With reference to FIG. 4, a cross sectional view of a bipolar platechannel coated with a plurality of titanium oxide/carbon layers isprovided. Flow field plate 12′ is coated with titanium oxide/carbonbilayers 54 ¹, 54 ², 54 ³ each of which are of the design set forthabove for titanium oxide/carbon layer 54. In this design, layers 50 ¹,50 ², 50 ³ are carbon layers and 52 ¹, 52 ², 52 ³ are titanium layers.The titanium oxide/carbon bilayer furthest from the metal plate istypically activated as set forth above. Although the specific example ofFIG. 4 includes three titanium oxide/carbon bilayers, it should beappreciated that this variation can include two titanium oxide/carbonbilayers. Moreover, the present variation may also include four or moretitanium oxide/carbon bilayers.

As set forth above, various embodiments of the present invention includeone or more titanium oxide layers. The chemical nature of the titaniumnature includes various crystalline forms of titanium oxide, amorphoustitanium oxide, as well as materials with chemical formula TiO₂ and thetitanium suboxides, titanium oxide hydrate and mixtures thereof.Examples of the crystalline forms include, but are not limited to,rutile, anatase, and brookite.

With reference to FIG. 5, a pictorial flowchart illustrating anexemplary method of forming the flow field plates set forth above isprovided. In step a), metal plate 12 is pre-conditioned prior todeposition of carbon layer 50. During such preconditioning, oxides onthe surface of metal plate 12 are typically removed or at least reduced.Such pretreatment may include a cleaning step. In step b), carbon layer50 is deposited onto metal plate 12. The carbon layer may be formed by anumber of technologies known to those skilled in the art. Examples ofsuch technologies include, but are not limited to, sputtering (e.g.,magnetron, unbalanced magnetron, etc), chemical vapor deposition (“CVD”)(e.g., low pressure CVD, atmospheric CVD, plasma enhanced CVD, laserassisted CVD, etc), evaporation (thermal, e-beam, arc evaporation, etc.)and the like. U.S. Pat. No. 5,314,716 discloses a CVD technique forforming non-crystalline carbon films. The entire disclosure of thepatent is hereby incorporated by reference. In step c), titanium oxidelayer 52 is deposited onto carbon layer 50. The titanium oxide layer maybe formed by a number of technologies known to those skilled in the art.Examples of such technologies include, but are not limited to,sputtering (e.g., magnetron, unbalanced magnetron, etc), chemical vapordeposition (“CVD”) (e.g., low pressure CVD, atmospheric CVD, plasmaenhanced CVD, laser assisted CVD, etc), evaporation (thermal, e-beam,arc evaporation, etc.), sol-gel coating technologies, layer by layerdeposition process, and the like.

In step d), surface 56 of titanium oxide layer/carbon bilayer 54 isactivated. FIG. 5B depicts UV visible or plasma activation via highdensity plasma 100. It should also be appreciated that additionalmethods of activation may be utilized. Such methods include, but are notlimited to, chemical activation such as treatment (e.g., etching) of thesurface with an acid such as sulfuric acid, hydrofluoric acid, chromicacid, potassium permaganate, and the like.

In a variation of the present embodiment, the carbon layers and titaniumoxide layers are deposited by sputtering. In one refinement, the carbonlayers are deposited using a closed field unbalanced magnetron system.For this purpose, a variation of the method and apparatus is set forthin U.S. Pat. No. 6,726,993 (the '993 patent). The entire disclosure ofthe '993 patent is hereby incorporated by reference in its entirety.

With reference to FIG. 6, a refinement of a sputtering deposition systemfor depositing the carbon layers set forth above is provided. FIG. 6provides a schematic top view of the sputtering system. Sputteringsystem 102 includes deposition chamber 103 and sputtering targets 104,106, 108, 110 which are proximate to magnet sets 112, 114, 116, 118. Amagnetic field generated between the targets 104, 106, 108, 110 ischaracterized with field lines extending between the magnetrons forminga closed field. The closed field forms a barrier which prevents theescape of electrons within plasma containing area 122. Moreover, thisconfiguration promotes ionization in the space within the closed fieldwith increased ion bombardment intensity. High ion current density isthereby achieved. Substrate 124 (i.e., metal plate 12) is held onplatform 126 which rotates along direction d₁. Flipper 132 causesrotation of substrate 124 about direction d₂ during a cycle of platform126. When system 102 is utilized, pre-conditioning step a) isadvantageously performed by ion etching within deposition chamber 103.

In one variation of the present embodiment, graphite targets aresputtered in a chamber under the influence of a closed unbalancedmagnetron field. A useful sputtering system is the Teer UDP 650 system.Graphite targets are placed on strong magnetrons that may be sputteredat a current ranging from 5 A-50 A in a closed field magnetronarrangement. The pressure in the sputter chamber may range from 1×10⁻⁶to 1×10⁻⁴, a bias voltage of −400V to −20V, pulse width of 250nanosecond to 2,000 nanosecond, and pulse DC at frequency rate of 400KHz to 50 KHz, and argon flow rate of 200 sccm to 20 sccm for a timeperiod of 10 minutes to 500 minutes. In one refinement, the carbon filmis deposited in a thickness ranging from 5 nm to 1,000 nm. In anothervariation, the carbon film is deposited in a thickness ranging from 10nm to 50 nm. The titanium oxide layer is then sputter deposited onto thecarbon layer by using titanium target in the presence of anoxygen-containing gas to form the titanium oxide/carbon bilayer setforth above. Activation of the titanium oxide/carbon bilayer isadvantageously performed in the same sputtering chamber after thetitanium oxide layer is formed.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A flow field plate for fuel cell applications comprising: a metalplate having a first surface and a second surface, the first surfacedefining a plurality of channels for directing flow of a first gaseouscomposition; a carbon layer disposed over at least a portion of themetal plate; and a titanium oxide layer disposed over at least a portionof the carbon layer to form a titanium oxide/carbon bilayer.
 2. The flowfield plate of claim 1 wherein the titanium oxide-coated carbon layerhas a surface with a contact angle less than 40 degrees.
 3. The flowfield plate of claim 1 wherein the contact resistance is less than 40mohm-cm² when the flow field plate is sandwiched between carbon papersat 200 psi.
 4. The flow field plate of claim 1 wherein the titaniumoxide layer is selectively deposited on a plurality of walls of thechannels.
 5. The flow field plate of claim 1 further comprising one ormore additional titanium oxide/carbon bilayers disposed over at least aportion of the titanium oxide/carbon layer.
 6. The flow field plate ofclaim 1 wherein the titanium oxide layer includes hydrocarbons in anamount that is less than 40 weight percent of the total weight of thetitanium oxide layer.
 7. The flow field plate of claim 1 wherein thetitanium oxide layer includes hydrocarbons in an amount that is lessthan 20 weight percent of the total weight of the titanium oxide layer.8. The flow field plate of claim 1 wherein the carbon layer comprisesamorphous carbon.
 9. The flow field plate of claim 1 wherein the carbonlayer comprises crystalline carbon.
 10. The flow field plate of claim 8wherein the carbon layer has a surface including on average at least 5pores per cm².
 11. The flow field plate of claim 1 wherein the titaniumoxide layer comprises a component selected from the group consisting ofTiO₂ , titanium suboxides, titanium oxide hydrate and mixtures thereof.12. The flow field plate of claim 1 wherein the titanium oxide layercomprises an amphorous titanium oxide or a polycrystalline titaniumoxide.
 13. The flow field plate of claim 1 wherein the titaniumoxide/carbon bilayer is activated by a UV or plasma source to render thesurface clean and maintain hydrophilicity
 14. The flow field plate ofclaim 1 wherein the titanium oxide/carbon bilayer is activated byvisible light after treatment with a nitrogen-containg gas
 15. The flowfield plate of claim 1 wherein the titanium oxide/carbon bilayer ishydrolytically stable.
 16. The flow field plate of claim 1 wherein themetal plate has a second surface defining a second plurality of channelsfor directing flow of a second gaseous composition.
 17. The flow fieldplate of claim 1 wherein the second surface is a second non-crystallinecarbon layer.
 18. A fuel cell comprising: a first flow field platecomprising: a metal plate having a first surface and a second surface,the first surface defining a plurality of channels for directing flow ofa first gaseous composition; a carbon layer disposed over at least aportion of the metal plate; a titanium oxide layer disposed over atleast a portion of the carbon layer to form a titanium oxide/carbonbilayer; a first catalyst layer disposed over the first flow fieldplate; an ion conductor layer disposed over the first catalyst layer; asecond catalyst layer disposed over the ion conductor layer; and asecond flow field plate disposed over the second catalyst layer.
 19. Thefuel cell of claim 18 having a contact resistance less than 40 mohm-cm²when the flow field plate is sandwiched between carbon paper at 200 psi.20. The fuel cell of claim 18 wherein the carbon layer surface has acontact angle less than 30 degrees.
 21. The fuel cell of claim 18wherein the titanium oxide layer comprises a component selected from thegroup consisting of TiO₂, titanium suboxides, titanium oxide hydrate andmixtures thereof.
 22. A method of making a flow field plate comprising ametal plate having a first surface and a second surface, the firstsurface defining a plurality of channels for directing flow of a firstgaseous composition, a carbon layer disposed over at least a portion ofthe metal plate, and a titanium oxide layer disposed over at least aportion of the carbon layer to form a titanium oxide/carbon bilayer, themethod comprising: depositing a carbon layer on the metallic plate;depositing a titanium oxide layer over the carbon layer to form thetitanium oxide/carbon layer; and activating the titanium oxide/carbonlayer.
 23. The method of claim 22 wherein the carbon layer surface isactivated with a plasma.